Inside the 309
Pulling the central glass panel away from the chassis shows us the interior where you will build your components into. The top is already filled with EGO fans that are daisy-chained together, including the rear fan. This is a proprietary connection from InWin, and therefore if you want to add compatible fans, you will need to get InWin fans to match and work together.
The CPU cutout is adequate for cooler backplates, the one area that I am not a fan of is the limited cable passthroughs. There are a couple in the top fan mounting area. Still, the two elongated rectangular ones on the far edge of the motherboard mounting will require proper management to avoid a messy looking install.
Looking at the front of the 309 from the inside, we see that the panel is solid steel. There is no airflow pass through here or anything like that. This chassis is designed to have the front closed off, and therefore airflow comes in from the bottom and out the top and rear. Up front, we also see the three 2.5" drive mount locations with two trays included along the front edge.
Yes, this does mean your 2.5" SSD or HDD will be visible in the main chamber, so keep that in mind when making component choices. Adjacent to these mounts, we have vertical slits in the metal, which serve to mount the GPU support bracket, which we will see in the accessories soon.
Taking a closer look at the top fan and radiator mounting, we can see that the holes are slotted to allow finite adjustment of your cooling position, along with compatibility should you have a cooling solution that is not a standard hole spacing. This solution is also ideal for the EGO fans since they are daisy-chained, so you can adjust the fan position to best work with the cabling.
Also, of note here are the same plastic fan mounting, which holds well and can make it much easier to pull them slightly to adjust fan position then just press them back into the fan surround firmly. In the rear side, where we see these fasteners is also where the PSU will reside when installed.
The bottom cooling mounting is not slotted and fixed positioning. The hexagonal openings carry the aesthetic, but also should avoid inhibiting airflow. As you can see, the standoff and expansion slot location is a clear indication that any cooling device mounted down here will potentially inhibit the full slot population, so keep that in mind once again.